1. Field of the Invention
The present invention relates to a nitride semiconductor thin film and a method for growing the same. More particularly, the present invention relates to a nitride semiconductor thin film and a method for growing the same, wherein a plurality of grooves are formed on a substrate by partially etching the substrate, and leg portions for preventing longitudinal growth of a nitride semiconductor are formed within the grooves so that the nitride semiconductor thin film is grown laterally to cover top portions of the leg portions, thereby ensuring growth of a high quality nitride semiconductor thin film.
2. Background of the Related Art
Generally, nitride-based semiconductors are direct transition type semiconductors and have been applied to light emitting elements such as light emitting diodes (LEDs) and laser diodes (LDs). Further, studies on application of the semiconductors to high temperature, high frequency and high electric power electronic devices have actively been conducted. Recently, much more attention has been paid to such semiconductors according to increased demand on light emitting elements.
Such nitride semiconductor thin films are mainly grown on sapphire substrates that are stable in high temperature.
However, since nitride semiconductor thin films and sapphire substrates have large differences in the lattice constants and the coefficients of thermal expansion, there are disadvantages in that a large number of defects such as threading dislocation are produced due to such large differences.
Thus, these defects cause a problem of the degradation of device properties.
Recently, in order to reduce defects in a sapphire substrate and a nitride semiconductor thin film, AlxGayIn1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1), SiN, or a stacked film on which these materials are stacked is formed into a buffer layer on a top surface of a sapphire substrate, and a nitride semiconductor thin film is then grown.
In this way, if a nitride semiconductor thin film is grown on the top of a buffer layer, the grown nitride semiconductor thin film has a low threading-dislocation density of 108-109 cm-2, thereby reducing a defect density.
Methods for reducing such threading dislocation include the following: 1) a method in which longitudinal growth and lateral growth are controlled by forming patterns on a sapphire substrate; 2) a lateral epitaxial overgrowth (LEO) method in which a nitride semiconductor thin film is grown on a top surface of a sapphire substrate, a certain pattern of a dielectric film is formed on the top of the nitride semiconductor thin film, and the nitride semiconductor thin film is then grown again; and 3) a Pendeo growth method in which a nitride semiconductor thin film is grown on a top surface of a sapphire substrate, etched in a certain pattern and then grown again.
Meanwhile, in order to fabricate blue violet LDs, or high output, high efficiency and high reliability LEDs, it is required to more reduce a defect density and to develop a method for growing a high quality nitride semiconductor thin film with a remarkably low defect density.